Norwich, 4th August 2016 – 6 Alpha Associates (6 Alpha), a specialist risk consultancy practice with expertise in the assessment and management of unexploded ordnance (UXO), has identified and managed the safe clearance of an inoperative chemical mine from a site at Horsham St Faith, a former RAF airfield.

The routine removal was part of work delivered by the company in accordance with a long-term contract with Norfolk County Council and Balfour Beatty, a British multinational infrastructure group, for the Norwich Northern Distributor Road (NDR) development.

Discovery of unexploded munitions at the sites of large-scale infrastructure and construction projects remains a common occurrence across the UK. A high proportion of UXO finds take place at former airfield sites, where a hazardous legacy has often been left behind by military activities, especially those conducted during WWII.

Faced with this threat to the safe and timely completion of infrastructure projects of this nature, thorough UXO survey and risk mitigation procedures form an essential part of early-stage project work prior to construction, particularly in those areas that have been afforded a high UXO risk rating.

The Horsham St Faith mine is likely to have been laid in the 1940s and it was probably intended to serve as an anti-invasion device, at a time when the perceived threat of invasion was at its highest. Clearance operations were implemented following the war to remove such devices, but those that were missed by those operations continue to be discovered.

Prior to the commencement of work on the NDR project, 6 Alpha Associates was engaged by Norfolk County Council and Balfour Beatty to complete a six-month UXO survey and mitigation contract to identify any on-site threats and manage their safe avoidance or removal.

As part of this ongoing work, the mine was subsequently discovered via a magnetometer survey, approximately 1-2m below ground. Upon further investigation, it was identified by 6 Alpha Associates as a Mk 1 Chemical mine, initially produced around 1914, but adapted for use during WWII as an ‘area denial’ weapon.

The mine had already been effectively neutralised and was empty when discovered. It is likely that the contents – which may have been incendiary or illumination type fill – had previously been allowed to dissipate as a result of ploughing activity, which had punctured the outer casing. This enabled 6 Alpha Associates to co-ordinate its safe removal from the site, in line with industry best practice.

“This was a comparatively unusual find,” said Robin Rickard, Programme Manager at 6 Alpha Associates. “Chemical weapons pose a very different hazard to conventional unexploded ordnance, and detonation must be avoided in order to prevent the discharge of harmful contents.”

“However, following our initial non-intrusive survey and a subsequent investigation of the site, our team not only located and carefully excavated it but also concluded that the device posed no risk to ongoing project work, and it has now been removed from the site.”

6 Alpha Associates has previously been engaged to manage UXO risks for a number of nationally significant infrastructure projects, including the Crossrail tunnelling project under central London – Europe’s largest railway and infrastructure construction project. 6 Alpha’s work was highly commended by the developer.